The no follow tag was introduced in 2005 to stop comment spams in blogs.
Most newbie bloggers don’t know what is no follow tag. Some bloggers know that what is no follow tag, but they don’t know how to use it. Don’t set almost every external links as no follow links.
After checking this post you may want to change many external links as no follow links. If your blog in WordPress platform you can use Ultimate Nofollow or Nofollow for external link plugin to do it easily.
When you optimize your posts for SEO no follow tag is also a very important tag.
This infographic is created by Search Engine Land.